Problem: can't initialize a variable from array length

Hi all!
I recently started using blueprints in UE 4.18 and using some videotutorials to wrap up some ideas and functionalities because i want to learn and improve, but I’ve got a problem.
I’m trying to read the array length created from “Get All Actors of Class” node and then put the array length into an integer variable, setting the new variable value.
The problem is that the variable doesn’t get updated, so even if I have 15 actors of the same class in the map, the varialbe value remains 0 instead of being initialized to 15…and I can’t get why this happens!